31 July 2008
Long term reductions in airborne heavy metals
Since many heavy metals, including lead and iron, can be harmful to human health at high
concentrations, their atmospheric levels are monitored. The UK Heavy Metals Monitoring
Network has been monitoring ambient metals for 25 years, and during that time there has been a
steady reduction in the levels of most metals in the air – with a few important exceptions.
Airborne metals are produced by the burning of fossil fuels and many heavy industrial processes, such as cement
production. As fuel use has changed and industry modernised to meet emission reduction targets, pollution with
many metal species has decreased. However, changes in metal use, for example the use of platinum in catalytic
converters which are now incorporated into most car engines, means that continuous environmental monitoring
remains important.
A critical examination of the UK Heavy Metals Monitoring Network, shows that it has not only provided data about air
quality, but has informed environmental policy-making: allowing scientists to gauge what the most important
pollutants are, and assess whether air pollution reduction targets are being met.
The UK network comprises 17 sites across the country, and similar networks are now in operation throughout the
developed world. The data produced by the sites is returned to the government who use it to assess compliance
with air quality legislation. The data are also submitted to the European Commission who assess UK compliance
with EC air quality directives.
According to the researchers, the data collected over the past two decades could also be used to inform the next
generation of policy making. The data have been compared with toxicology data, which will enable metals with the
greatest health impacts to be prioritised and more closely monitored.
Analysis of the longitudinal data shows that levels of iron, mercury and lead have steadily decreased, in line with
legislative targets and changes in fuel use. The data also show that ambient air levels of lead, nickel, arsenic,
cadmium and mercury are now below the target limits set through European legislation at all sites in the network.
Although further reductions in the levels of these metals are anticipated over the next few years, they will level off as
background levels are approached. Levels of copper and chromium, however, have remained fairly stable over the
monitoring period.
The research team has cautioned that the network cannot provide data that represents the complete set of all
metals present in air. And, over the years, the number and the location of the monitoring sites have changed – to
cover new emission sources and to assess the most representative population exposure. This means that the
average values produced for the UK from year to year have an element of variability imposed upon them.
In the future, as the adverse health effects of more metals are recognised, or as their emissions to air increase, the
network will be in a position to respond to changing priorities. This will involve the use of new, improved monitoring
techniques, which will require governments to invest in the future of environmental monitoring.
Source: Brown, R.J., Yardley, R.E., Muhunthan, D. et al. (2008). Twenty-five years of nationwide ambient metals measurement in the United
Kingdom: concentration levels and trends. Environmental Monitoring and Assessment. 142 (1-3): 127-140.
Contact: [email protected]
Theme(s): Air pollution
Opinions expressed in this News Alert do not necessarily reflect those of the European Commission
To cite this article/service: "Science for Environment Policy": European Commission DG Environment News Alert Service, edited by
SCU, The University of the West of England, Bristol.
European Commission DG ENV
News Alert Issue 118
July 2008
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